Changing the ending (spoilers)
One thing I felt needed to be sold better was Ellie's change of heart at the very end. She is driven almost irrationally by her revenge quest the entire game. Suddenly a memory of Joel on the porch randomly pops in her head as she is murderously drowning Abby, which causes her to let go seconds before she is about to "accomplish her mission". Although I was personally glad she let Abby go, it just didn't feel fully earned.
One idea: Cut back to the theater encounter. This time, Ellie is able to get the upper hand on Abby. She has her switchblade at her throat, while Dina is holding Lev down. Just as she is about to slice Abby's throat, Lev cries out and begs Ellie not to kill her. Ellie suddenly flashes back to Joel's death, thinking of herself pleading with Abby not to kill Joel, seeing a mirror of herself in Lev. In that moment, she realizes she had allowed herself to become the monster she was hunting and chooses to release Abby. Abby tries to retaliate but similar to the actual game, she sees Lev look in horror and disapproval, causing her to regain her humanity in that moment. Ellie and Abby then mutually accept moving on and putting the past behind. Lev and Abby proceed to Santa Barbara, while Ellie (with all fingers intact), Dina and JJ get their version of a happy ending in Jackson.